This invention relates to the assembly of self-locking retaining rings. More particularly, this invention relates to the assembly of self-locking retaining rings having a plurality of circumferentially spaced locking prongs projecting from a ring body.
Internal and external retaining rings having a narrow gap and which are equipped with lugs on both sides of the gap are generally assembled and disassembled by means of pliers. Many retaining rings with a wide gap such as E-Rings are assembled by means of fork-like applicators, and some types and sizes are assembled by means of magazine fed assembly tools.
The foregoing types of assembly tools are not suitable for the assembly of closed self-locking rings. Prior to the present invention only rather primitive tubular plungers for assembly of such self-locking rings have seen widespread use notwithstanding the fact that closed self-locking rings have been manufactured for decades.
One such application tool for use in connection with external, closed self-locking rings comprises a tubular plunger having a front end with a recessed groove in which the ring may be magnetically seated. The tubular plunger is employed to place the ring over the shaft on which it is to be mounted. For assembly of internal, closed self-locking rings it has been suggested that a mandrel be employed to effect entry into the housing bore in which the ring is to be positioned.
Although such primitive tools may be acceptable for some purposes, they are not entirely desirable for a number of reasons.
For example, if the rings are accidentally misaligned with the shaft or housing onto or into which they will be installed during assembly, such misalignment is aggravated by unequal forces acting on the locking prongs. As a result, some of the prongs may be severely deformed during installation, and the assembled ring will not withstand the required load.
In addition, since the tools are arranged so that the ring itself first enters the housing or is placed over the shaft, it had become commonplace to employ rings where the locking prongs were inclined to provide a lead-in for the ring assembly. With such rings, however, it is imperative that the ring be oriented for assembly with the prongs inclined away from the assembly direction. Otherwise prong breakage will almost certainly occur and the assembly will have to be repaired or discarded.
Accordingly, it is important to employ reasonably skilled persons to handle the assembly operation with the rather primitive prior art tools, and even then the process of appropriately centering and orienting the ring can be quite time consuming and hence costly.
In a prior U.S. Pat. No. 2,885,770, issued May 12, 1959 to the assignee of the present invention, there has been proposed a somewhat more sophisticated tool for assembling a particular type of closed, internal self-locking retaining rings. The tool disclosed in that patent contemplates the provision of a cup-shaped body member having an outer diameter corresponding to the diameter of the bore into which the ring is to be assembled and presenting an open-end edge on which the ring is to be seated prior to assembly. Also contemplated is the provision of means for releasably securing the ring seated on the open edge. This means is to take the form of a disc member that abuts the body member, three equidistantly spaced arms slidable within slots in the body member, and spring fingers accommodated by recesses and slots in the arms.
A single tool of this type lacks ready adaptability to rings of different size, and the machining of an acceptable tool for smaller ring sizes on the order of one-half inch or the like would be extremely difficult if not impossible.
In addition to complications that can be envisioned as associated with the reliable manufacturing of such a tool with a complex configuration of the disc, arms and slots, and the apparent limited utility of the tool to a particular type of internal self-locking retaining ring, it will be appreciated that several operational difficulties could also be encountered.
For example, since the spring fingers are flexed during ring seating and ring release, there is a danger that after a period of use the intended centering of the ring would be defeated by reasons of nonuniform flexure and bias characteristics of the springs being induced. Similar misalignment problems could occur because of damage to the spring fingers, which are exposed, during normal handling of the tool. Moreover, even without such difficulties, problems with the reliability of initial spring uniformity and/or positioning of the spring fingers, coupled with the ability of the ring to undergo significant radial displacement during its assembly, could produce misalignment problems, and attendant adverse consequences of the type discussed above in connection with primitive tools actually in use today.
Further complications of this type could be induced by the particular arrangement disclosed for biasing the disc arms and spring assembly into engagement with the body member. Limited deflection characteristics of the biasing spring, its external tool location and the tolerances which it must take up might produce additional unreliability.